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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Poperechny I. S., Krasikov A. A., Semenov S. V., Popkov S. I., Knyazev Yu. V., Kirillov V. L., Yakushkin S. S., Martyanov O. N., Raikher Y. L.
Заглавие : Dynamic remagnetisation of CoFe2O4 nanoparticles: thermal fluctuational thawing of anisotropy
Коллективы : [AAAA-A17-117103050081-1]; [AAAAA20-120020690030-5]
Место публикации : J. Phys. D. - 2021. - Vol. 54, Is. 27. - Ст.275003. - ISSN 0022-3727, DOI 10.1088/1361-6463/abf371. - ISSN 1361-6463(eISSN)
Примечания : Cited References: 63. - Experimental measurements were supported by Project No. AAAA-A17-117103050081-1. I S P and Yu L R acknowledge the support of ICMM in the framework of topical task AAAAA20-120020690030-5. The numerical calculations were performed on the Uran supercomputer (Ural Branch, Russian Academy of Sciences, Ekaterinburg)
Предметные рубрики: COBALT-FERRITE NANOPARTICLES
MAGNETIC-PROPERTIES
SIZE
COERCIVITY
Аннотация: We report a study of the magnetodynamics of cobalt ferrite (CoFe2O4) nanoparticles with an average diameter of ~6 nm. Hysteresis loops were measured under quasi-static conditions and in pulse fields with amplitudes H0 of up to 130 kOe and for durations τP of 8 and 16 ms. The growth of coercivity Hc observed with an increase in the magnetic field variation rate dH/dt (determined by the values of H0 and τP) and the reduction of Hc with temperature is ascribed to the superparamagnetic effect. The proposed theoretical model explains the observed dependences fairly well. Notably, the effective magnetic anisotropy constant obtained exceeds the value for bulk crystals and might be indicative of the contribution of surface magnetic anisotropy.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gokhfeld D. M., Semenov S. V., Terentyev K. Yu., Yakimov I. S., Balaev D. A.
Заглавие : Interplay of magnetic and superconducting subsystems in Ho-doped YBCO
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk Territory, Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, project "Superconducting properties of YBCO incorporated by paramagnetic rare-earth elements" [20-42-240008]
Место публикации : J. Supercond. Nov. Magn. - 2021. - Vol. 34. Is. 10. - P.2537-2543. - ISSN 1557-1939, DOI 10.1007/s10948-021-05954-3. - ISSN 1557-1947(eISSN)
Примечания : Cited References: 26. - This work was supported by the Russian Foundation for Basic Research and the Government of the Krasnoyarsk Territory, Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, project "Superconducting properties of YBCO incorporated by paramagnetic rare-earth elements" No. 20-42-240008
Предметные рубрики: TEMPERATURE
TRANSPORT
PEAK
DY
SUSCEPTIBILITY
TRANSITION
BEHAVIOR
Аннотация: Superconducting and paramagnetic contributions to the magnetization of polycrystalline Y1−xHoxBa2Cu3O7−δ samples were investigated. The superconductivity is responsible for a partial screening of magnetic ions from an external magnetic field and for a possible sinking of antiferromagnetic correlations between these ions. Magnetic moments of Ho ions influence on a peak effect induced by the order–disorder transition of the Abrikosov vortex lattice. The critical current density and the critical temperature of YBCO are not changed by the Ho doping.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Semenov S. V., Varnakov S. N., Radionov E. Y., Tretyakov Al. Y.
Заглавие : High-temperature evolution of the magnetization of aluminum reduction cell steel
Место публикации : J. Sib. Fed. Univ. Math. Phys. - 2021. - Vol. 14, Is. 1. - P.5-11. - ISSN 19971397 (ISSN), DOI 10.17516/1997-1397-2021-14-1-5-11; Журн. СФУ. Матем. и физика
Примечания : Cited References: 17. - We are grateful to A. D. Balaev and S. V.Komogortsev for fruitful discussions. The magnetic measurements were performed on the facility at the Krasnoyarsk Territorial Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences. This study was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk Territory, the Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, and the United Company RUSAL, project no. 20-48-242905 "Determining the Effect of Magnetization of Ferromagnets on the MHD Parameters of the Reduction Cell"
Аннотация: The magnetic properties of steel of a structural element of an aluminum reduction cell have been investigated in the temperature range of 300–900 K. The analysis of the temperature dependence of the saturation magnetization Ms(T) showed (i) the applicability of the Bloch’s 3/2 law and a reason- able value of the Bloch’s constant for steel and (ii) the quadratic dependence Ms(T)~(1 - T2) in the temperature range of 380–700 K.В работе исследованы магнитные свойства стали конструктивного элемента алюминиевого электролизера в области температур 300–900 K. Проведенный анализ температурной зависимости намагниченности насыщения MS(T) показал: (i) применимость "закона 3/2" Блоха, а также разумное значение константы Блоха и константы обменного взаимодействия для стали; (ii) квадратичную зависимость MS(T)∼(1 - T2) в температурном диапазоне 380–700 K.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Freidman A. L., Semenov S. V., Kolkov M. I., Terent'ev K. Yu., Pavlovskiy N. S., Gokhfeld D. M., Shaykhutdinov K. A., Balaev D. A.
Заглавие : Inverse and direct magnetoelectric effects in orthorhombic DyMnO3 manganite single crystals
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science [18-42-243024]
Место публикации : J. Appl. Phys. - 2020. - Vol. 128, Is. 9. - Ст.094102. - ISSN 0021-8979, DOI 10.1063/5.0006595. - ISSN 1089-7550(eISSN)
Примечания : Cited References: 27. - The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project "Research, synthesis and investigation of new oxide single crystals showing the interrelation of magnetic, magnetoelastic and magnetoelectric properties" (Project No. 18-42-243024). The measurements were performed in part on the equipment at the Krasnoyarsk Territorial Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences
Аннотация: Correlations between the direct and inverse magnetoelectric effects in orthorhombic DyMnO3 single crystals have been investigated. In the inverse magnetoelectric effect, the magnetic moment of the crystal appears to have a contribution that is sinusoidal oscillating in ac electric fields below the temperature TFE of ferroelectric phase transition. The first and the second harmonics of the inverse magnetoelectric effect are clearly detected. The magnetoelectric susceptibilities α and β, corresponding to first and second harmonics, are found to correlate with the derivative of polarization with respect to the magnetic field. The influence of the magnetic and electric regimes during cooling on magnetoelectric effects has also been studied. The maximum change in the magnetic moment of a sample under the action of electric fields is observed under the same (T, H) conditions as the rotation of the spontaneous polarization vector from the crystallographic c direction to the a axis in the magnetic field H || b.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Semenov S. V., Gokhfeld D. M.
Заглавие : New evidence of interaction between grain and boundaries subsystems in granular high-temperature superconductors
Место публикации : J. Supercond. Novel Magn. - 2021. - Vol. 34. Is. 4. - P.1067-1075. - ISSN 15571939 (ISSN), DOI 10.1007/s10948-021-05812-2
Примечания : Cited References: 62
Аннотация: Granular high-temperature superconductors (HTSs) exhibit magnetotransport properties, including the clockwise magnetoresistance hysteresis. The hysteresis is explained by the concept of an effective field in the subsystem of grain boundaries, where the observed dissipation occurs. The effective field in the intergrain medium is determined by a superposition of the external field H and the field induced by the magnetic response of HTS grains. The magnetic flux compression in the intergrain medium provides an increase of the effective field. The magnetoresistance hysteresis of polycrystalline YBa2Cu3O7-δ has a bright feature: In a fairly wide external field range, the hysteresis width ΔH(H) is found to be almost linear, ΔH ≈ H. This behavior is considered to be universal over the entire temperature range corresponding to the superconducting state (the investigations have been carried out at temperatures of 77 K and 4.2 K). The analysis of the magnetoresistive and magnetic properties has shown that the upper boundary of the field range of the ΔH ≈ H regime is consistent with the field of complete penetration into HTS grains. This is indicative of the strong interrelation between the magnetotransport and magnetic properties of granular HTSs.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fomenko E. V., Anshits N. N., Solovyov L. A., Knyazev Yu. V., Semenov S. V., Bayukov O. A., Anshits A. G.
Заглавие : Magnetic fractions of PM2.5, PM2.5-10, and PM10 from coal fly ash as environmental pollutants
Место публикации : ACS Omega. - 2021. - Vol. 6, Is. 30. - P.20076-20085. - ISSN 24701343 (ISSN), DOI 10.1021/acsomega.1c03187
Примечания : Cited References: 59. - This work was conducted within the framework of the budget project # 121031500198-3 for Institute of Chemistry and Chemical Technology SB RAS using for SEM–EDS and magnetic studies the equipment of Krasnoyarsk Regional Research Equipment Centre of SB RAS
Аннотация: Characterization of magnetic particulate matter (PM) in coal fly ashes is critical to assessing the health risks associated with industrial coal combustion and for future applications of fine fractions that will minimize solid waste pollution. In this study, magnetic narrow fractions of fine ferrospheres related to environmentally hazardous PM2.5, PM2.5–10, and PM10 were for the first time separated from fly ash produced during combustion of Ekibastuz coal. It was determined that the average diameter of globules in narrow fractions is 1, 2, 3, and 7 μm. The major components of chemical composition are Fe2O3 (57–60) wt %, SiO2 (25–28 wt %), and Al2O3 (10–12 wt %). The phase composition is represented by crystalline phases, including ferrospinel, α-Fe2O3, ε-Fe2O3, mullite, and quartz, as well as the amorphous glass phase. Mössbauer spectroscopy and magnetic measurements confirmed the formation of nanoscale particles of ε-Fe2O3. Stabilization of the ε-Fe2O3 metastable phase, with quite ideal distribution of iron cations, occurs in the glass matrix due to the rapid cooling of fine globules during their formation from mineral components of coal.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Semenov S. V., Gokhfel'd D. M., Terent'ev K. Yu., Balaev D. A.
Заглавие : Mechanisms of the magnetoresistance hysteresis in a granular HTS with the paramagnetic contribution by the example of HoBa2Cu3O7-δ
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk krai; Krasnoyarsk Territorial Foundation for Support of Scientific and RD Activities [20-42-240008]
Место публикации : Phys. Solid State. - 2021. - Vol. 63, Is. 12. - P.1785-1794. - ISSN 1063-7834, DOI 10.1134/S1063783421100334. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 72. - This study was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk krai, and the Krasnoyarsk Territorial Foundation for Support of Scientific and R&D Activities, project no. 20-42-240008 "Effect of introduction of paramagnetic ions of rare-earth elements on the superconducting properties of YBCO materials"
Предметные рубрики: HIGH-TEMPERATURE SUPERCONDUCTOR
MAGNETIC-FLUX COMPRESSION
Аннотация: The hysteretic behavior of magnetoresistance R(H) of the granular high-temperature superconductor (HTS) HoBa2Cu3O7 – δ has been investigated. The YBCO superconductors with a rare-earth element (Nd, Ho, Er, Sm, Yb, or Dy) with the magnetic moment in the yttrium site are characterized by a significant paramagnetic contribution to the total magnetization. The main goal of this study has been to establish the possible effect of this paramagnetic contribution on the magnetotransport properties, which are determined by tunneling of superconducting current carriers through the grain boundaries. An analysis of the results obtained basing on the concept of an effective field in the intergrain medium showed that the distribution of the magnetic induction lines from the paramagnetic moments is fundamentally different from that of the Meissner currents and Abrikosov vortices. The magnetic induction lines from the paramagnetic moments are not concentrated in the region of grain boundaries and therefore insignificantly affect the magnetotransport properties of a granular HTS. At the same time, the magnetic induction lines are strongly concentrated in the grain boundaries, which is caused by the Meissner currents and Abrikosov vortices, due to the features of their properties. Specifically, the magnetic flux compression determines the magnetotransport (in particular, the R(H) hysteresis) properties of granular HTSs, including 1–2–3 ones, with a rare-earth ion with the magnetic moment.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shaykhutdinov K. A., Balaev D. A., Semenov S. V., Popkov S. I., Dubrovskiy A. A., Sapronova N. V., Volkov N. V.
Заглавие : Relaxation of low-temperature magnetoresistance and magnetization of polycrystalline (La0.5Eu0.5)0.7Pb 0.3MnO3
Место публикации : Journal of Physics D: Applied Physics. - 2011. - Т. 44, № 25. - С. 255001. - ISSN 0022-3727, DOI 10.1088/0022-3727/44/25/255001. - ISSN 1361-6463(eissn)
РИНЦ
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Semenov S. V., Balaev D. A., Petrov M. I.
Заглавие : Universal behavior and temperature evolution of the magnetoresistance hysteresis in granular high-temperature superconductors Y-Ba-Cu-O
Место публикации : Phys. Solid State. - 2021. - Vol. 63, Is. 7. - P.1069-1080. - ISSN 1063-7834, DOI 10.1134/S1063783421070192. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 80. - The authors are grateful to D.M. Gokhfeld for discussion of the results. The measurements of the transport properties were performed in part on a PPMS-6000 system of the Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch of the Russian Academy of Sciences
Предметные рубрики: CRITICAL-CURRENT-DENSITY
CURRENT-VOLTAGE CHARACTERISTICS
MAGNETIC-FLUX COMPRESSION
Аннотация: Regularities in the behavior of the magnetoresistance hysteresis R(H) in the granular yttrium high-temperature superconductors (HTSs) have been established. For this purpose, a comparative analysis of the magnetotransport properties has been carried out on the granular HTS samples, which exhibit (i) approximately the same magnetic properties and temperatures of the onset of the superconducting transition (90.5–93.5 K, which is characteristic of HTS grains) and (ii) different critical transport currents JC (which is characteristic of grain boundaries). Despite a significant (by more than an order of magnitude) spread of the JC values for the three samples, a universal behavior of the magnetoresistance hysteresis has been found, which is apparently inherent in all the granular Y–Ba–Cu–O compounds. The R(H) hysteresis is extremely broad and, in a fairly wide external field range, the dependence of the magnetoresistance hysteresis width ΔН on the field Hdec (the external field for the decreasing hysteresis branch is Н = Hdec) is almost linear: ΔH ≈ Hdec. This behavior is observed over the entire temperature range of implementation of the superconducting state (the investigations have been carried out at temperatures of 77–88 and 4.2 K). The result obtained has been explained by considering the effective field in grain boundaries, which is a superposition of the external field and the field induced by the magnetic moments of grains. The field induced by grains, in turn, significantly increases in the region of grain boundaries due to the magnetic flux compression (the grain boundary length is shorter than the HTS grain size by several orders of magnitude). The aforesaid has been confirmed by the analysis of the R(H) hysteresis for the Y–Ba–Cu–O- and CuO-based HTS composite, in which the grain boundary length is purposefully increased; as a result, the flux compression is less pronounced and the R(H) hysteresis narrows.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Popkov S. I., Semenov S. V., Volochaev M. N., Velikanov D. A., Kirillov V. L., Martyanov O. N.
Заглавие : Uncompensated magnetic moment and surface and size effects in few-nanometer antiferromagnetic NiO particles
Место публикации : J. Magn. Magn. Mater. - 2021. - Vol. 539. - Ст.168343. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2021.168343
Примечания : Cited References: 98. - The TEM study was carried out on the equipment of the Krasnoyarsk Territorial Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences
Аннотация: The analysis of the M(H) magnetization curves of antiferromagnetic nanoparticles yields information about magnetic subsystems formed in these objects, which are characterized by a large fraction of surface atoms. However, in the conventionally investigated experimental magnetic field range of up to 60–90 kOe, this analysis often faces the ambiguity of distinguishing the Langevin function-simulated contribution of uncompensated magnetic moments μun of particles against the background of a linear-in-field dependence (the antiferromagnetic susceptibility and other contributions). Here, this problem has been solved using a pulsed technique, which makes it possible to significantly broaden the range of external fields in which the μun contribution approaches the saturation. Nanoparticles of a typical NiO antiferromagnet with an average size of d ~ 4.5 nm have been investigated. Based on the thorough examination of the M(H) magnetization curves measured in pulsed fields of up to 250 kOe, a model of the magnetic state of NiO nanoparticles of such a small size has been proposed. The average moment is ~130 μB (μB is the Bohr magneton) per particle, which corresponds to 60–70 decompensated spins of nickel atoms localized, according to the Néel hypothesis (μun ~ d3/2), both on the surface and in the bulk of a particle. A part of the surface spins unrelated to the antiferromagnetic core form another subsystem, which behaves as free paramagnetic atoms. Along with the antiferromagnetic core, an additional linear-in-field contribution has been detected, which is apparently related to superantiferromagnetism, i.e., the size effect inherent to small antiferromagnetic particles.
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11.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Balaev D. A., Poperechny I. S., Krasikov A. A., Semenov S. V., Popkov S. I., Knyazev Yu. V., Kirillov V. L., Yakushkin S. S., Martyanov O., Raikher Y. L.
Заглавие : Superparamagnetic effect on the dynamic remagnetization of CoFe2O4 nanoparticles in a pulse field
Коллективы : International Baltic Conference on Magnetism: focus on nanobiomedicine and smart materials, Балтийский федеральный университет им. И. Канта
Место публикации : 4th International Baltic Conference on Magnetism (IBCM 2021): Book of abstracts. - 2021. - P.104
Примечания : Cited References: 7
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12.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Balaev D. A., Dubrovskiy A. A., Semenov S. V., Krasikov A. A., Knyazev Yu. V., Bayukov O. A., Yakushkin S. S., Kirillov V. L., Bukhtiyarova G. A., Martyanov O. A.
Заглавие : Unusual magnetic behavior of polymorph iron oxide ϵ-Fe2O3 nanoparticles: magnetic phase diagram and surface effects
Коллективы : Российская академия наук, Уральское отделение РАН, Институт физики металлов им. М. Н. Михеева Уральского отделения РАН, Уральский федеральный университет им. первого Президента России Б.Н. Ельцина, Российский фонд фундаментальных исследований, Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium
Место публикации : Euro-asian symposium "Trends in magnetism" (EASTMAG-2019): Book of abstracts/ чл. конс. ком.: S. G. Ovchinnikov, N. V. Volkov [et al.] ; чл. прогр. ком. D. M. Dzebisashvili [et al.]. - 2019. - Vol. 2. - Ст.J.I2. - P.164-165. - ISBN 978-5-9500855-7-4 (Шифр В33/E12-125657784)
Примечания : Cited References: 15. - This work was supported by the Russian Science Foundation, project no. 17-12-01111
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13.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Semenov S. V., Balaev A. D., Balaev D. A.
Заглавие : New approach to describing dissipation in granular HTSs
Коллективы : Российская академия наук, Уральское отделение РАН, Институт физики металлов им. М. Н. Михеева Уральского отделения РАН, Уральский федеральный университет им. первого Президента России Б.Н. Ельцина, Российский фонд фундаментальных исследований, Euro-Asian Symposium "Trends in MAGnetism", "Trends in MAGnetism", Euro-Asian Symposium
Место публикации : Euro-asian symposium "Trends in magnetism" (EASTMAG-2019): Book of abstracts/ чл. конс. ком.: S. G. Ovchinnikov, N. V. Volkov [et al.] ; чл. прогр. ком. D. M. Dzebisashvili [et al.]. - 2019. - Vol. 2. - Ст.I.P13. - P.159. - ISBN 978-5-9500855-7-4 (Шифр В33/E12-125657784)
Примечания : Cited References: 4. - The work was supported by the Russian Science Foundation (Grant No. 17-72-10050)
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Chumakov A. I., Dubrovskiy A. A., Semenov S. V., Yakushkin S. S., Kirillov V. L., Martyanov O. N., Balaev D. A.
Заглавие : Mössbauer Study of the Magnetic Transition in ϵ-Fe2O3 Nanoparticles Using Synchrotron and Radionuclide Sources
Место публикации : JETP Letters. - 2019. - Vol. 110, Is. 9. - P.613-617. - ISSN 00213640 (ISSN), DOI 10.1134/S0021364019210082
Примечания : Cited References: 23. - This work was supported by the Russian Science Foundation (project no. 17-12-01111)
Аннотация: Nuclear γ-resonance experiments with energy and time resolved detection are carried out with ϵ-F2O3 nanoparticles and a 57Co(Rh) laboratory Mössbauer source of γ radiation and a 14.4125 keV synchrotron radiation source on the ID18 beamline (ESRF) in the temperature range of 4–300 K. Both methods show a tremendous increase in the hyperfine field in tetrahedrally coordinated iron positions during the magnetic transition in the range of 80–150 K. As a result, the splitting of the quantum beat peaks in the nuclear scattering spectra is observed in the time interval of 20–170 ns with a periodicity of ∼ 30 ns. In addition, the first quantum beat is slightly shifted to shorter times. A correlation between the quadrupole shift and the orbital angular momentum of iron in ϵ-F2O3 nanoparticles is found. The magnetic transition leads to the rotation of the magnetic moment in the tetrahedral positions of iron around the axis of the electric field gradient by an angle of 44°.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Knyazev Yu. V., Yakushkin S. S., Balaev D. A., Dubrovskiy A. A., Semenov S. V., Bayukov O. A., Kirillov V. L., Martyanov O. N.
Заглавие : Magnetic Properties of Ultrafine ε-Fe2O3 Nanoparticles in a Silicon Xerogel Matrix
Место публикации : Bull. Russ. Acad. Sci. Phys. - 2019. - Vol. 83, Is. 7. - P.875-877. - ISSN 10628738 (ISSN), DOI 10.3103/S1062873819070219
Примечания : Cited References: 11
Аннотация: A new metamaterial is obtained on the basis of ε-Fe2O3 nanoparticles immobilized in a xerogel matrix. Samples are synthesized by impregnating SiO2 hydrogel with iron (II) salts with subsequent drying and calcination. The structure and magnetic properties of the composites are probed using transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, and static magnetic measurements. © 2019, Allerton Press, Inc.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dubrovskiy A. A., Semenov S. V., Knyazev Yu. V., Popkov S. I., Yakushkin S., Kirillov V., Martyanov O., Balaev D. A.
Заглавие : The Low-Temperature Magnetic State and Magnetic Ordering Temperature of ϵ-Fe2O3 Iron Oxide Nanoparticles
Место публикации : IEEE Magn. Lett. - 2019. - Vol. 10. - Ст.6110103. - ISSN 1949307X (ISSN), DOI 10.1109/LMAG.2019.2956674
Примечания : Cited References: 22
Предметные рубрики: Magnetic resonance
Magnetic hysteresis
Temperature distribution
Saturation magnetization
Nanoparticles
Perpendicular magnetic anisotropy
Аннотация: The ϵ-Fe2O3 iron oxide polymorph is a well-known magnetic material with a complex magnetic structure, which undergoes a series of magnetic transitions in different temperature ranges. However, the ϵ-Fe2O3 phase diagram is still unclear. We report on the magnetic properties of a sample consisting of ϵ-Fe2O3 nanoparticles with an average size of 8 nm embedded in a SiO2 xerogel matrix without an admixture of foreign phases. Along with the features typical of the well-known ϵ-Fe2O3 magnetic transition in the temperature range 80–150 K, the temperature dependence of magnetization M(T) of ϵ-Fe2O3 includes other low-temperature anomalies. In an external field of H = 70 kOe, there is a noticeable temperature hysteresis of magnetization at 50–90 K, and near T ≈ 50 K, the M(T) curves have a characteristic bending, which may be indicative of an additional magnetic transition. The ferromagnetic resonance spectra shows that, near 500 K, a magnetic phase transition occurs, which was previously thought to be a transition to the paramagnetic state. An analysis of the temperature dependence of the ferromagnetic resonance spectra shows that the magnetically ordered phase in ϵ-Fe2O3 exists up to about 800 K.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Semenov S. V., Dubrovskii A. A., Krasikov A. A., Popkov S. I., Yakushkin S. S., Kirillov V. L., Mart'yanov O. N.
Заглавие : Synthesis and magnetic properties of the core-shell Fe3O4/CoFe2O4 nanoparticles
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [17-12-01111]
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 2. - P.285-290. - ISSN 1063-7834, DOI 10.1134/S1063783420020043. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 37. - This study was supported by the Russian Science Foundation, project no. 17-12-01111.
Предметные рубрики: MOSSBAUER
ENSEMBLE
Аннотация: The Fe3O4/CoFe2O4 nanoparticles with a core-shell structure with an average size of 5 nm have been obtained by codeposition from the iron and cobalt chloride solutions. An analysis of the magnetic properties of the obtained system and their comparison with the data for single-phase Fe3O4 (4 nm) and CoFe2O4 (6 nm) nanoparticles has led to the conclusion about a noticeable interaction between the soft magnetic (Fe3O4) and hard magnetic (CoFe2O4) phases forming the core and shell of hybrid particles.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Popkov S. I., Dubrovskiy A. A., Semenov S. V., Velikanov D. A., Kirillov V. L., Martyanov O. N.
Заглавие : Features of the quasi-static and dynamic magnetization switching in NiO nanoparticles: Manifestation of the interaction between magnetic subsystems in antiferromagnetic nanoparticles
Место публикации : J. Magn. Magn. Mater. - 2020. - Vol. 515. - Ст.167307. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2020.167307
Примечания : Cited References: 89. - We are grateful to A.D. Balaev for fruitful discussions. The TEM study and magnetic measurements using a PPMS-6000 facility were carried out on the equipment of the Krasnoyarsk Territorial Center for Collective Use, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences
Аннотация: We report on the investigations of a system of 8-nm NiO particles representing antiferromagnetic (AFM) materials, which are weak magnetic in the form of submicron particles, but can be considered to be magnetoactive in the form of nanoparticles due to the formation of the uncompensated magnetic moment in them. The regularities of the behavior of magnetization switching in AFM nanoparticles are established by studying the magnetic hysteresis loops under standard quasi-static conditions and in a quasi-sinusoidal pulsed field of up to 130 kOe with pulse lengths of 4–16 ms. The magnetic hysteresis loops are characterized by the strong fields of the irreversible magnetization behavior, which is especially pronounced upon pulsed field-induced magnetization switching. Under the pulsed field-induced magnetization switching conditions, which are analogous to the dynamic magnetic hysteresis, the coercivity increases with an increase in the maximum applied field H0 and a decrease in the pulse length. This behavior is explained by considering the flipping of magnetic moments of particles in an external ac magnetic field; however, in contrast to the case of single-domain ferro- and ferrimagnetic particles, the external field variation rate dH/dt is not a universal parameter uniquely determining the coercivity. At the dynamic magnetization switching in AFM nanoparticles, the H0 value plays a much more important role. The results obtained are indicative of the complex dynamics of the interaction between magnetic subsystems formed in AFM nanoparticles.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popkov S. I., Krasikov A. A., Semenov S. V., Dubrovskii A. A., Yakushkin S. S., Kirillov V. L., Mart'yanov O. N., Balaev D. A.
Заглавие : General regularities and differences in the behavior of the dynamic magnetization switching of ferrimagnetic (CoFe2O4) and antiferromagnetic (NiO) nanoparticles
Коллективы : Russian Foundation for Basic ResearchRussian Foundation for Basic Research (RFBR); Government of the Krasnoyarsk region; Krasnoyarsk Regional Foundation for Science [18-42-240012]
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 9. - P.1518-1524. - ISSN 1063-7834, DOI 10.1134/S1063783420090255. - ISSN 1090-6460(eISSN)
Примечания : Cited References: 46. - This work was supported by the Russian Foundation for Basic Research, the Government of the Krasnoyarsk region, and the Krasnoyarsk Regional Foundation for Science, project no. 18-42-240012: "Magnetization switching of magnetic nanoparticles in strong pulsed magnetic fields is a new approach to studying the dynamic effects related to the processes of magnetization of magnetic nanoparticles"
Предметные рубрики: PARTICLE-SIZE
EXCHANGE-BIAS
TEMPERATURE
STATE
COERCIVITY
Аннотация: In antiferromagnetic (AFM) nanoparticles, an additional ferromagnetic phase forms and leads to the appearance in AFM nanoparticles of a noncompensated magnetic moment and the magnetic properties typical of common FM nanoparticles. In this work, to reveal the regularities and differences of the dynamic magnetization switching in FM and AFM nanoparticles, the typical representatives of such materials are studied: CoFe2O4 and NiO nanoparticles with average sizes 6 and 8 nm, respectively. The high fields of the irreversible behavior of the magnetizations of these samples determine the necessity of using strong pulsed fields (amplitude to 130 kOe) to eliminate the effect of the partial hysteresis loop when studying the dynamic magnetic hysteresis. For both types of the samples, coercive force HC at the dynamic magnetization switching is markedly higher than HC at quasi-static conditions. HC increases as the pulse duration τP decreases and the maximum applied field H0 increases. The dependence of HC on field variation rate dH/dt = H0/2τP is a unambiguous function for CoFe2O4 nanoparticles, and it is precisely such a behavior is expected from a system of single-domain FM nanoparticles. At the same time, for AFM NiO nanoparticles, the coercive force is no longer an unambiguous function of dH/dt, and the value of applied field H0 influences more substantially. Such a difference in the behaviors of FM and AFM nanoparticles is caused by the interaction of the FM subsystem and the AFM “core” inside AFM nanoparticles. This circumstance should be taken into account when developing the theory of dynamic hysteresis of the AFM nanoparticles and also to take into account their practical application.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Semenov S. V., Balaev D. A.
Заглавие : Model of the behavior of a granular HTS in an external magnetic field: temperature evolution of the magnetoresistance hysteresis
Место публикации : Phys. Solid State. - 2020. - Vol. 62, Is. 7. - P.1136-1144. - ISSN 10637834 (ISSN), DOI 10.1134/S1063783420070239
Примечания : Cited References: 61. - The authors are grateful to D.M. Gokhfeld for discussion of the results. The measurements of the transport properties were performed in part on a PPMS-6000 facility at the Krasnoyarsk Territorial Center of Collective Use, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences
Аннотация: A model for describing the magnetoresistance behavior in a granular high-temperature superconductor (HTS) that has been developed in the last decade explains a fairly extraordinary form of the hysteretic R(H) dependences at T = const and their hysteretic features, including the local maximum, the negative magnetoresistance region, and the local minimum. In the framework of this model, the effective field Beff in the intergrain medium has been considered, which represents a superposition of the external field and the field induced by the magnetic moments of HTS grains. This field can be written in the form Beff(H) = H + 4παM(H), where M(H) is the experimental field dependence of the magnetization and α is the parameter of crowding of the magnetic induction lines in the intergrain medium. Therefore, the magnetoresistance is a function of not simply an external field, but also the “internal” effective field R(H) = f(Beff(H)). The magnetoresistance of the granular YBa2Cu3O7 – δ HTS has been investigated in a wide temperature range. The experimental hysteretic R(H) dependences obtained in the high -temperature range (77–90 K) are well explained using the developed model and the parameter α is 20–25. However, at a temperature of 4.2 K, no local extrema are observed, although the expression for Beff(H) predicts them and the parameter α somewhat increases (~30–35) at this temperature. An additional factor that must be taken into account in this model can be the redistribution of the microscopic current trajectories, which also affects the dissipation in the intergrain medium. At low temperatures under the strong magnetic flux compression (α ~ 30–35), the microscopic trajectories of the current Im can change and tunneling through the neighboring grain is preferred, but the angle between Im and Beff will be noticeably smaller than 90°, although the external (and effective) field direction is perpendicular to the macroscopic current direction.
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